The invention relates to a corona ignition device of the type generally known from EP 1 662 626 A1. Such corona ignition devices have, at their end remote from the combustion chamber, a plug connector with which they can be connected to a high-frequency generator or the on-board power supply system of a vehicle.
It is known from EP 1 662 626 A1 and WO 2004/063560 A1 how a fuel/air mixture in a combustion chamber of an internal combustion engine can be ignited by a corona discharge produced in the combustion chamber by a corona ignition device. The corona ignition device has a center electrode that is stuck in an insulator. The center electrode is thus electrically insulated with respect to a housing of the corona ignition device and the walls of the combustion chamber, which are at ground potential. The center electrode forms a capacitor together with the housing or the walls of the combustion chamber. Therein the housing and the walls of the combustion chamber act as a counter electrode of the capacitor.
This capacitor, together with a coil arranged in the housing, forms an electric oscillating circuit which is excited by a high-frequency voltage, which for example is produced with the aid of a transformer with center tap or another high-frequency generator. When the oscillating circuit is excited resonantly, there is a voltage step-up between the center electrode and the walls of the combustion chamber or the housing of the corona ignition device. This leads to the formation of a corona discharge in the combustion chamber. The corona discharge originates from an ignition tip on the center electrode.
Compared to conventional spark plugs, which ignite fuel/air mixtures by means of arc discharges, corona ignition devices have the advantage of a much lower burn-up of the electrodes or ignition tips. Corona ignition devices therefore have the potential of a much longer service life compared to conventional spark plugs.